The present invention relates to a thin film transistor liquid crystal display (TFT LCD).
Among the various flat panel display technologies, TFT LCDs are dominating the flat panel display market due to lower power consumption, relatively low manufacturing cost, no radiation, etc. A TFT LCD can be formed by assembling an array substrate and a color filter substrate with a liquid crystal layer interposed therebetween. Post spacers are typically formed on the color filter substrate to maintain a cell gap between the substrates.
FIG. 1a is a schematic view showing a conventional TFT LCD. As shown in FIG. 1a, there are a plurality of gate lines 1, a plurality of common electrodes 12, and a plurality of data lines 5 perpendicular to the gate lines 1 on the array substrate of the TFT LCD. The adjacent gate lines and data lines cross with each other to define pixel areas. Each pixel area comprises a TFT switching device, a transparent pixel electrode 10, two light blocking bars 11, and a part of the common electrode 12. FIG. 2a is a schematic view of the color filter of the TFT LCD shown in FIG. 1a. As shown in FIG. 2a, there are a black matrix 14 and color filters 15 of primary colors such as red, green, and blue on the color filter substrate of the TFT LCD. Each color filter 15 corresponds to one pixel area on the array substrate. Post spacers 13 are arranged uniformly across the color filter substrate. The post spacers 13 are located above the TFT switching device after the assembling of the substrates.
As shown in FIG. 1b, the TFT switching device comprises a gate electrode 2, a gate insulating layer 4, a semiconducting active layer 3, and a source electrode 6 and a drain electrode 7. A transparent electrode 10 is connected with the drain electrode 7 of the TFT device via a through-hole 9 in a passivation layer 8. The top end of post spacer 13 is pressed against the TFT device. It can be seen that since the post spacer 13 contacts the TFT substrate on the TFT device, the highest position of the TFT array substrate, the post spacer tends to be moved to a lower position under pressure or upon impact, and also it is difficult for the post spacer to return to the original position once being moved, thus causing light leakage. Thus caused poor performance will significantly affect the yield as well as the display quality of the TFT LCD.